My (24M) dad (52M) found a disposable vape in my sister's backpack ( 18f).

Now he's asking for both of us to do nicotine tests because he suspects we've been smoking. I get it if he's suspicious of my sister, but i didn't do anything. I just got dragged into this. He got nothing tangible in order to accuse me.

And as a matter of fact i now my sis doesn't smoke it was just a broken vape that she found in class. But that brings me to the question of why should i do it?

I simply told him that i won't do it, since legally he can't force me. i told him that if do it then i won't ever speak to him again because he broke the trust.

For info, he went ahead and told all family members that he caught us smoking. I'm just asking for an advice on how to hold my ground as i simply refuse to do it. Ps: sorry for English I'm not native